In the production of many paper products, such as tissue and towel products, paper webs are typically formed in a paper making system and initially stored in large parent rolls. The parent rolls are unwound for finishing operations, such as embossing, printing, ply attachment, perforating, and the like and then rewound into retail-sized logs or rolls.
Unwinding and further processing parent rolls made from paper webs, particularly soft and high bulk tissue webs, can be challenging due to the fact that the product can easily break or become damaged. Unwinding such rolls in a fast and efficient manner can also be problematical. For instance, in many traditional operations, parent rolls are unwound one roll at a time. After a parent roll is unwound, the machine is stopped for the removal of the core and deployment of a new parent roll. The downtime associated with parent roll changeovers, creates a substantial reduction in total available run time that reduces the maximum output that can be obtained from a rewinder line.
A center driven unwind system that has provided great improvements in systems and processes for unwinding parent rolls is disclosed in U.S. Pat. No. 5,906,333 to Fortuna, et al. and U.S. Pat. No. 6,030,496 to Baggot, et al., which are incorporated herein by reference in their entireties. In the above patents, a system is disclosed which includes a pair of horizontally spaced apart side frames. Each side frame includes an elongated arm capable of engaging a parent roll. The elongated arms are operably associated with variable speed drive means for unwinding the parent roll. Once the parent roll is partially unwound, the arms move the parent roll to a core placement table which rotatably supports the partially unwound roll. The elongated arms then move away from the core placement table to engage a second parent roll. A leading end portion of the web on the second parent roll is bonded to a trailing end of the partially unwound first parent roll to form a joined web.
Although the above system has provided great advancements, further improvements are still needed in the handling and unwinding of parent rolls. In particular, a need exists for a system capable of unwinding multiple parent rolls without a significant amount of down time. Further improvements are also needed for systems that can unwind high bulk tissue webs without breaking or otherwise damaging the webs as they are unwound.
In general, the present invention is directed to a system and method for unwinding rolls of material. The system and process of the present invention can be used to unwind various different types of materials. The system, however, is particularly well suited to unwinding paper webs, especially soft, high bulk tissue webs. Without damaging the webs.
In one embodiment, the unwind system of the present invention includes a frame defining a primary unwind location and a secondary unwind location. A first drive device adapted to engage a center position of a roll of material to be unwound is positioned to engage the roll of material when the roll of material is in the primary unwind location. As used herein, the xe2x80x9ccenter portionxe2x80x9d of a roll of material generally refers to whatever object or device the material is wound around and can include, for instance, a core, a spool, or the material itself in a coreless roll. The system further includes a second drive device adapted to engage an outside surface of the roll of material when the roll of material is in the primary unwind location. The second drive device operates in conjunction with the first drive device to unwind the roll of material. For instance, the first drive device can be a center unwind device, while the second drive device can be a surface unwind device. The second drive device can include a driven belt that is movable between a roll engagement position and a non-engagement position. In one embodiment, the second drive device is used in conjunction with the first drive device to initially unwind the material. Once the roll of material has reached a preselected unwind speed, however, the second drive device can then be disengaged. In this manner, the second drive device can be used to accelerate the roll of material without causing any material breakage.
The system of the present invention can further include a transfer mechanism that transfers the roll of material from the primary unwind location to the secondary unwind location after a portion of the material has been unwound from the roll. A third drive device is positioned at the secondary unwind location and is configured to further unwind the roll of material after the roll of material has been transferred to the secondary unwind location.
In one embodiment, the first drive device is configured to move with the roll of material from the primary unwind location to the secondary unwind location while continuously unwinding the roll. Once transferred to the secondary unwind location, the first drive device can disengage the roll and return to the primary unwind location, while unwinding is continued at the secondary location by the third drive device.
In an alternative embodiment, the second drive device moves with the roll of material from the primary unwind location to the secondary unwind location for continuous unwinding during the transfer.
The third drive device can be a center unwind device that engages a core or spool of the roll of material that is to be unwound or, alternatively, can be a surface unwind device that engages a surface of the roll of material that is to be unwound. In one embodiment, the third drive device can be configured to move from the secondary unwind location to the primary unwind location to engage a roll of material and continuously unwind the material while the material is being transferred to the secondary unwind location, as opposed to using the first drive device or the second drive device.
As described above, when transferring a roll of material from the primary unwind location to the secondary unwind location, one of the drive devices can be used to continuously unwind the roll. It should be understood, however, that in one embodiment of the present invention, the roll of material can be transferred from the primary unwind location to the secondary unwind location without continuous unwinding. In fact, since the primary unwind location and the secondary unwind location are relatively closely spaced together, such a small interruption in the unwinding process will not significantly effect the efficiency of the system.
Once a roll of material is partially unwound and transferred from the primary unwind location to the secondary unwind location, a second roll of material can be placed in the primary unwind location for subsequent unwinding. In this regard, the system of the present invention can include an air jet nozzle for emitting air onto a leading end of the second roll of material positioned at the primary unwind location. The air jet nozzle can blow the leading end of the second web onto the first web being unwound at the secondary unwind location. Once the leading end of the second roll of material is placed on top of the first roll of material being unwound, the plies can be attached together through pressure or the use of an adhesive. Once attached together, unwinding of the first roll of material can be ceased causing the material to break. Continuous unwinding of the second roll of material can then commence while the remains of the first roll of material can be removed from the system.
In one embodiment of the present invention, the frame can include a staging area and a collecting area in addition to the primary unwind location and the secondary unwind location. Rolls of material to be unwound can be kept in the staging area for transfer to the primary unwind location. For example, in one embodiment, the first drive device can be configured to move to the staging area and engage a roll of material and move with the roll of material to the primary unwind location.
The collecting area can collect the unwound cores or spools of the rolls of material. Once ejected from the secondary unwind location, the remainder of the unwound rolls of material can be fed by gravity to the collecting area.
Although the relative location of the different areas on the frame can be changed as desired, in one embodiment, the staging area can be located generally at the same elevation as the primary unwind location. The secondary unwind location, on the other hand, can be positioned below the primary unwind location. The collecting area can be positioned at an elevation lower than the secondary unwind location and generally below the staging area.
If desired, the system of the present invention can be completely automated. For instance, the system can include a controller, such as a microprocessor or a programmable logic unit. The controller can be used to control all of the drive devices for unwinding a roll according to the process of the present invention. In order to automate the system, the system can include various sensors for indicating when it is time to transfer rolls from one location to the next. For example, in one embodiment, the system can include a roll diameter sensor that sends information to the controller. The roll diameter sensor can sense information about the diameter of a roll being unwound in the primary unwind location. Once the roll reaches a predetermined diameter, the controller can be used to automatically transfer the roll to the secondary unwind location.
A speed sensor can also be incorporated into the system for determining the unwind speed of a roll of material in the primary unwind location. The speed sensor can be used to indicate when it is time to engage or disengage the second drive device.
Other features, and aspects of the present invention are discussed in greater detail below.